The physicist's gray matter has been sitting in a cookie jar for half a century. What does it really reveal about human genius?

After suffering an aortic aneurysm on April 13, 1955, Albert Einstein became the subject of an international deathwatch. He succumbed to internal hemorrhaging at 1:15 AM on April 18. His body arrived shortly thereafter at a hospital in Princeton, New Jersey, for a routine autopsy. That's when the pathologist on duty, Thomas Harvey, faced a stark choice.

Any one of us might have been tempted the same way- who wouldn't want to know what in Einstein's brain made him Einstein? The genius himself expressed interest in having his mind studied and analyzed after he died, and he even sat for brain scans. In the end, though, he decided against preserving the best part of himself because he loathed the thought of people venerating it, the 20th-century equivalent of a medieval Catholic relic. But as Harvey arranged the scalpels in his autopsy room that night, he knew humankind had just one chance to salvage the gray matter of the greatest scientific thinker in centuries. By 8 AM the next morning -without next-of-kin permission and against Einstein's wish for cremation- Harvey had, shall we say, liberated the physicist's brain and released the body to the family without it.

The disappointments started immediately. Einstein's brain weighed 43 ounces, at the low end of normal. And before Harvey could measure anything more, word of the relic spread. During a discussion about Einstein in school the next day, Harvey's son, normally a laconic lad, blurted out, "My dad's got his brain!" A day later, newspapers across the country mentioned Harvey's plans in their front-page obits. Harvey did eventually convince the remaining Einsteins, who were understandably peeved, to grant permission for further study. So after measuring its dimensions with calipers and photographing it for posterity, Harvey sawed the brain into 240 taffy-sized hunks and lacquered each one in celloidin. Soon, he was mailing the blobs in mayo jars to neurologists, confidence that the forthcoming scientific insights would justify his peccadillo.

But over the course of the next 40 years, neurologists ended up publishing only three papers on Einstein's brain. Most found nothing extraordinary. Harvey kept soliciting scientists to take another look, but the brain chunks mostly just sat around, wrapped in cheesecloth and tucked into wide-mouthed glass cookie jars of formaldehyde broth. The jars themselves sat in a cardboard box in Harvey's office, tucked behind a red beer cooler. When Harvey lost his job and took off for greener pastures in Kansas (where he was neighbors with William S. Burroughs), the brain rode shotgun in his car.

In the past 15 years, though, Harvey's persistence has been justified, a little. A few cautious papers have highlighted some atypical aspects of Einstein's brain, on both microscopic and macroscopic levels. Coupled with research into the genetics of brain growth, these findings may yet provide some insight into what separates human brains from animal brains and what pushes an Einstein a few standard deviations beyond that.

Early attempts to find the biological basis of intelligence were based on the idea that bigger was better: More brain mass meant more thinking power, just more muscles meant more lifting power. This theory had its shortcomings; sperm whales and their 17-pound brains don't dominate the globe. Today, the obsession with overall brain size had given way to obsessing over the size of various parts of the brain. Primates have particularly beefy neuron shafts (called axons) compared with other animals and can therefore send information through each neuron more quickly. Even more important is the thickness of the cortex, the outermost brain layer, which promotes thinking and dreaming and other flowery pursuits. Scientists know that certain genes are crucial for growing a thick cortex, partly because it's so sadly obvious when these genes fail. And Einstein's cortex had a few unusual features.

One study found that, compared with normal older men, Einstein had the same number of neurons and had the same average neuron size. However, his prefrontal cortex was thinner, which gave him a greater density of neurons tucked into the space. Closely packed neurons may help the brain process information more quickly -a tantalizing find considering that the prefrontal cortex orchestrates thoughts throughout the brain and helps solve multistep problems.

Further studies examined certain folds and grooves in Einstein's cortex. As with brain size, it's a myth that simply having more folds automatically makes a brain more potent. But folding does generally indicate higher functioning. Smaller and dumber monkeys, for instance, have fewer corrugations in their cortexes. So do newborn humans. That means that as we mature from infants to young adults and as the genes that wrinkle our brains start kicking in, every one of us relives millions of years of human evolution! Scientists also know that a lack of brain folds is devastating. The genetic disorder "smooth brain" leaves babies severely underdeveloped, if they even survive to term. Instead of being succulently furrowed, a smooth brain looks eerily polished, and cross-sections of it, instead of showing scrunched-up brain fabric, look like slabs of liver.

But what about the fact that Einstein often though about physics mostly through pictures? He famously declared, for example, that he formulated relativity theory in part by imagining what would happen if he rode around bareback on light rays. Perhaps that's due to the unusual wrinkles and ridges in the cortex of his parietal lobe, a region that aids in both mathematical reasoning and image processing. The Parietal lobe also integrates sound, sight, and other sensory input into the rest of the brain's thinking. Einstein once said that abstract concepts only achieved meaning in his mind "through their connection with sense-experiences." Indeed, his family remembers him practicing his violin whenever he got stuck on a physics problem. An hour later, he'd often declare, "I've got it!" and return to work. Auditory input seemed to jog his thinking. The parietal ridges and wrinkles in Einstein's lobes were steroid thick, 15 percent bigger than normal. And whereas most of us mental weaklings have skinny right parietal lobes and even skinnier left parietal lobes, Einstein's were equally buff.

Strangest of all, however, is the fact that Einstein seemed to be missing part of his middle brain, the parietal operculum; at the very least, it didn't develop fully. This part of the brain helps produce language, and its absence might explain why Einstein didn't speak until age two and why until age seven he had to rehearse every sentence he spoke aloud under his breath. But there might have been compensations. This region normally contains a small gap, and our thoughts have the ability to get routed the long way around. This quirk in Einstein's brain might have meant that he could process certain information more speedily, by bringing two separate parts of his brain into unusually direct contact.

All of which is exciting. But is it exciting bunkum?

Einstein feared his brain becoming a relic. But have we done something equally silly and reverted to phrenology? To be certain, Einstein wasn't the first autopsy of a celebrity. Doctors set aside Beethoven's temporal bones in 1827 to study his deafness, but a medical orderly nicked them. The Soviet Union founded an entire institute in part to study Lenin's brain and determine what makes a revolutionary a revolutionary. Similarly, and despite the body being mutilated by mobs, Americans helped themselves to half of Mussolini's brain after World war II to determine what makes a dictator.

Einstein's brain has deteriorated into chopped liver by now (it's even the same color), which forces today's scientists to work mostly from old photographs, a less precise method. And not to put a too fine point on it, but Thomas Harvey coauthored half of the various studies on the "extraordinary" features of Einstein's brain, and he certainly had an interest in science learning something from the organ he purloined. It's possible that Einstein's features are idiosyncratic and had nothing to do with genius; it's hard to tell with a sample size of one. Even trickier, we can't sort out whether usual neuro-features (like thickened parietal folds) caused Einstein's genius or whether his genius allowed him to "exercise" and build up those parts of his brain. But even if Einstein's genius remains enigmatic, scientists have sussed out a lot about the everyday genius of humans.

For example, they now know that a mutation in humans a few million years ago deactivated a gene that bulked up our jaw muscles. This probably allowed us to get by with thinner skulls, which in turn freed up precious space in the skull for brain expansion. Another surprise was that apoE, the gene that made us meat eaters, helped the brain manage cholesterol, which is major component of myelin. To function properly, the brain needs to sheath its axon in myelin, which acts like rubber insulation and prevents signals from short-circuiting or misfiring.

Even more fascinating is the fact that scientists have recently detected 3,181 base pairs of "junk DNA" in chimpanzee's brains that got deleted in humans. This region helps stop out-of-control neuron growth, which can lead to big brains, obviously, but also brain tumors. Human, it turns out, gambled in deleting this DNA, but the risk paid off, and our brains ballooned. Today, the breakthroughs in neuroscience are coming faster and faster. And while scientists still can't pinpoint what makes an Einstein an Einstein, they do know that with DNA it's not always what we gained that makes us human; sometimes it's what we lost.